Signaling system



Sept. 2 19324 15%,736-

L. DGRFMAN SIGNALING SYSTEM Filed Aug. 5. 1921 l 0 l I.

WITNESSES: INVENTOR 5% L50 Duff/rm.

ATTORN EY Patented Sept. 2, 1924.

UNITED STATES 1,566,736 PATENT OFFICE.

LEO nonnivrAN, on wILKINsBURe, PnNNsYLv NIA, ssmN P'. To wEs'rINeH'onsn ELECTRIC & MANUFACTURING COMPANY, A. CORPORATION or PENNSYLVANIA.

SIGNALING SYSTEM.

Application filed August 3, 1921.

an antenna without making any physical change in the main-antenna circuit.

Another object of my invention is to provide means for controlling the effective capacity of a main antenna by the use of an auxiliary or control antenna.

A still further object of my invention is to change the amount of energy received by the antenna from the source of oscillations without materially varying the wavelength of the antenna output.

In sending messages where used to break the antenna circuit, arcing has been a serious problem. In other cases where the energy has been diverted into another circuit, the adjustment of the circuits toinsure efficient operation has proved difficult;

In my system, I employ an antenna circuit coupled to a continuous-wave source of radio-frequency current. The antenna circuit is tuned to the frequency of the continuous-wave source- To prevent radiation I make use of an auxiliary antenna, preferably located beneath and substantially parallel to the main antenna, which is adapted to afiect the main antenna to change its effective capacity. This I accomplish by connecting the auxiliary antenna to ground. The effective height of the main antenna is'thereby varied. A key normally connects the auxiliary antenna to ground, and the main antenna operates to transmit messages only upon depression of the key.

The insertion of the auxiliary antenna between the main antenna and ground operates to greatly reduce the amount of energy received by the main-antenna circuit from the continuous-wave source of radio-frequency current.

keys have been Serial No. 489,448.

trates diagrammatically a sending system embodying the principles of my invention;

In the drawing, a main antenna 1 is connected, through a variable induction coil2, to the ground. In this case, the distributed capacity of the antenna is presumed to be" suflicient to furnish the necessary capacity for tuning the circuit to the desired fre'- quency. Coupled to the induction coil 2 is a variable-induction coil 3, contained within a circuit having a variable condenser 4 and a continuouswave source of radiofrequency alternations 5. The circuit within which the-radio-frequency source 5 lies is tuned to resonance with the frequency of the source. The source of radio-frequency alternations may be any continuous-wave radio-frequency source, such as a thermionic oscillator, a high-frequency alternator, etc.

WVhile I have shown such a system for coupling the main antenna circuit to the continuous-wave source of radio-frequency oscillations, it is to-be understood that any method of coupling the circuits may be employed and that the particular system which I have illustrated is solely for the purpose of explanation.

Located below the main antenna 1 and substantially parallel thereto, is an auxiliary antenna 6. The ground lead from the'auxiliary antenna 6 passes to a contact member 7 adapted to normally engage an arm 8 of a telegraphic key 9. The key 9 is pivoted and grounded at 11 and the other arm 12 of the key is held in an up position by means of a spring 13. Stops 14 and 15 limit the downward movement of the arms 8 and 12, respectively.

When the circuit of the auxiliary antenna 6 is open, the main antenna system, comprising the antenna 1 and the variable induction coil 2, is tuned to the frequency of the continuous-wave source 5. Therefore, under such conditions the antenna" 1 radiates continuous-wave oscillations of'the" frequency of the source 5. However, since the auxiliary antenna 6 lies below the antenna 1 and substantially parallel thereto and is normally in circuit with the ground, the effective capacity of the antenna 1 is changed, and the main antenna SyStefillS, therefore, no longer in tune with the continuous-wave source 5. This greatly reduces the amount of energy received by the;- main antenna system, since but a srfiall then resonant to the frequency of the con tinuous-wave source 5, and oscillations will be sent out while the key is depressed. Upon release of pressure on the key 9 the spring 13 causes the arm 8 of the key to make contact with contact member 7 in the lead from the auxiliary antenna 6, and the auxiliary antenna is again connected to ground, thereby changing the resonant frequency of the main antenna system so that oscillations of the sending frequency are no longer emitted.

By employing an auxiliary antenna to change the effective capacity of the main antenna, I effect a great change the amount of'energy received from th continuous-wave source, whereby substantially no energy will be radiated while the auxiliary antenna is connected to ground, and, moreover, what small energy is radiated will have its frequency changed to some frequency other than the sending frequency. My system likewise permits the power output from an antenna to be controlled without altering or disturbing the main-antenna circuit.

Since I have not shown all of the possible modifications of my invention which could be conceived by one skilled in the art, I desire that my invention shall be limited solely .by the prior art and the scope of the appended claims.

I claim as my invention:

1. A method of changing the resonant frequency of an antenna which consists in changing the effective height of the antenna leaving the physical height unaltered.

2. A method of changing the resonant frequency of an antenna which consists in connecting a neighboring antenna to ground and thereby changing the effective height of the first antenna.

3. A method of changing the capacity of a main antenna comprising locating an auxiliary antenna below the main antenna and connecting the auxiliary antenna to the ground.

4. A method of sending radio messages comprising the steps of tuning a main sending antenna to a desired frequency, locating an auxiliary antenna below the main antenna, connecting said auxiliary antenna to the. ground and making and breaking said connection in accordance with the message.

5. A variable antenna comprising a main antenna, an auxiliary antenna located below the main antenna, .and switching means associated with the auxiliary antenna for making and breaking a connection to ground, whereby the capacity of the main antenna may be Varied.

V 6. A sending system' comprisinga continuous-wave source of radio-frequency oscillations, an antenna tuned to the frequency of the source and coupled thereto, and means for varying the effective height of the antenna leaving the physical height unaltered.

7. A sending system comprising a continuous-source of radio-frequency oscillations, a main antenna tuned to the same frequency as the source and coupled thereto, a grounded auxiliary-antenna circuit including an auxiliary antenna below said main antenna and a key in the auxiliary-antenna circuit to make and break the connection to ground, whereby the effective capacity of the main antenna may be varied.

8. A method of sending radio signals comprising the steps of tuning an antenna to the sending frequency, coupling it to a continuous-wave source of the sending frequency, locating an auxiliary antenna within influencing distance of the first antenna and Varying the energy output of the antenna by changing the connections of the circuit, of an auxiliary circuit connecting.

the antenna to ground, said auxiliary circuit having greater capacity than the nor-V mal capacity of the antenna with respect to ground, and modulating means in said auxiliary circuit.

11. The combination with a tuned antenna circuit, of an auxiliary circuit connecting said antenna to ground, said auxiliary circuit having capacitive impedance, and modulating means in said auxiliary circuit. r

12. In a radio sending system, a flat-to antenna, means for causing the same to radiate, and means for checking said radiation, comprising a second flat-top antenna thetop of which is below and electrostatically coupled to the top of the first-mentioned antenna. I

18. In combination, two flat-top antennae, a source of undamped radio-frequency energy in one of said antennae and a switch in the other, the said antenna being electrostatically coupled and the frequency of said source being that for which its antenna is resonant when the switch is open.

1 1. A means for altering the period of a. flat-topped antenna, comprising a horizontal conducting body electrostatically coupled to the top of said antenna, and a separable connection between said body and the ground. 15. A means for altering the period of a 6 flat-topped antenna, comprising a horizontal conducting body electrostatically coupled to the top of said antenna and the area of Which is of the same order of magnitude as said top, and a separable connection between said body and the ground.

In testimony whereof, I have hereunto subscribed my name this 27th day of July, 1921.

LEO DORFMA'N. 

